This invention relates to boron coated abrasives, a process for their production, and to boron coated abrasives for use in saw blade segments, grinding wheels and other abrasive-containing tools.
Abrasive particles such as diamond and cubic boron nitride are commonly used in cutting, grinding, drilling, sawing and polishing applications. In such applications, abrasive particles are mixed with metal powder mixes, then sintered at high temperatures to form bonded cutting elements. Typical bond matrices contain iron, cobalt, copper, nickel and/or alloys thereof.
Common problems in applications are retention of particles in the bond matrix, and resistance against oxidative attack during the sintering process and the subsequent application.
These problems are commonly addressed by coating the abrasive particles with metals or alloys which bond chemically to the particle, and alloy to the bond matrix. Typically, chemical vapour deposition (CVD) or physical vapour deposition (PVD sputter coating) techniques are used. A disadvantage of the CVD technique is that it often requires the use of highly toxic chemical compounds. A disadvantage of the PVD technique, being a low temperature technique, is that the metal coating does not form a chemical bond with the grit particles.
U.S. Pat. No. 6,524,357 discloses a process for coating a superabrasive with a metal by heating the superabrasive and a coat-forming powder in an inert atmosphere. It is a requirement of this process that the coating powder contains a metal compound of which the metal is thermally reducible by the superabrasive.
The addition of boron oxide and/or boric acid to diamond powder to manufacture sintered diamond compacts at high pressure and high temperature in order to improve the strength of the compact, for use in cutting and drilling applications, is disclosed in JP 9142 932. Similarly, EP 0 352 811 describes the use of metal-coated superabrasives for the high pressure high temperature manufacture of superabrasive cutting elements and compacts.
U.S. Pat. No. 4,902,652 discloses a method for producing diamond compacts at high pressure high temperature (i.e. in the region where diamond is stable) by using coated diamond particles. Although boron is mentioned as one of the coatings, only conventional techniques of ion sputtering and ion plating are disclosed.